Conventionally, as this type of equipment monitoring system, for example, in Patent Document 1 an equipment monitoring system is disclosed in which, in order to reduce the power consumption of a detector (a terminal device in Patent Document 1) while constantly monitoring monitored equipment, the detector performs an intermittent detection operation in which the detector is basically set to a sleep state, and at predetermined time intervals, the detector is set to an awake state and performs a detection operation, and after the detection operation is completed, the detector is set to the sleep state until performing the next detection operation.